mirror of
https://github.com/topjohnwu/Magisk.git
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364 lines
10 KiB
C++
364 lines
10 KiB
C++
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "system_properties/contexts_split.h"
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#include <ctype.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <async_safe/log.h>
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#include "system_properties/context_node.h"
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#include "system_properties/system_properties.h"
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class ContextListNode : public ContextNode {
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public:
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ContextListNode(ContextListNode* next, const char* context, const char* filename)
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: ContextNode(strdup(context), filename), next(next) {
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}
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~ContextListNode() {
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free(const_cast<char*>(context()));
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}
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ContextListNode* next;
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};
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struct PrefixNode {
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PrefixNode(struct PrefixNode* next, const char* prefix, ContextListNode* context)
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: prefix(strdup(prefix)), prefix_len(strlen(prefix)), context(context), next(next) {
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}
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~PrefixNode() {
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free(prefix);
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}
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char* prefix;
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const size_t prefix_len;
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ContextListNode* context;
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PrefixNode* next;
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};
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template <typename List, typename... Args>
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static inline void ListAdd(List** list, Args... args) {
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*list = new List(*list, args...);
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}
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static void ListAddAfterLen(PrefixNode** list, const char* prefix, ContextListNode* context) {
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size_t prefix_len = strlen(prefix);
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auto next_list = list;
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while (*next_list) {
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if ((*next_list)->prefix_len < prefix_len || (*next_list)->prefix[0] == '*') {
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ListAdd(next_list, prefix, context);
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return;
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}
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next_list = &(*next_list)->next;
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}
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ListAdd(next_list, prefix, context);
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}
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template <typename List, typename Func>
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static void ListForEach(List* list, Func func) {
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while (list) {
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func(list);
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list = list->next;
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}
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}
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template <typename List, typename Func>
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static List* ListFind(List* list, Func func) {
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while (list) {
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if (func(list)) {
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return list;
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}
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list = list->next;
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}
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return nullptr;
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}
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template <typename List>
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static void ListFree(List** list) {
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while (*list) {
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auto old_list = *list;
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*list = old_list->next;
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delete old_list;
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}
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}
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// The below two functions are duplicated from label_support.c in libselinux.
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// TODO: Find a location suitable for these functions such that both libc and
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// libselinux can share a common source file.
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// The read_spec_entries and read_spec_entry functions may be used to
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// replace sscanf to read entries from spec files. The file and
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// property services now use these.
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// Read an entry from a spec file (e.g. file_contexts)
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static inline int read_spec_entry(char** entry, char** ptr, int* len) {
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*entry = nullptr;
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char* tmp_buf = nullptr;
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while (isspace(**ptr) && **ptr != '\0') (*ptr)++;
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tmp_buf = *ptr;
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*len = 0;
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while (!isspace(**ptr) && **ptr != '\0') {
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(*ptr)++;
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(*len)++;
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}
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if (*len) {
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*entry = strndup(tmp_buf, *len);
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if (!*entry) return -1;
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}
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return 0;
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}
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// line_buf - Buffer containing the spec entries .
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// num_args - The number of spec parameter entries to process.
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// ... - A 'char **spec_entry' for each parameter.
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// returns - The number of items processed.
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//
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// This function calls read_spec_entry() to do the actual string processing.
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static int read_spec_entries(char* line_buf, int num_args, ...) {
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char **spec_entry, *buf_p;
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int len, rc, items, entry_len = 0;
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va_list ap;
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len = strlen(line_buf);
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if (line_buf[len - 1] == '\n')
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line_buf[len - 1] = '\0';
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else
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// Handle case if line not \n terminated by bumping
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// the len for the check below (as the line is NUL
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// terminated by getline(3))
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len++;
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buf_p = line_buf;
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while (isspace(*buf_p)) buf_p++;
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// Skip comment lines and empty lines.
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if (*buf_p == '#' || *buf_p == '\0') return 0;
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// Process the spec file entries
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va_start(ap, num_args);
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items = 0;
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while (items < num_args) {
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spec_entry = va_arg(ap, char**);
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if (len - 1 == buf_p - line_buf) {
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va_end(ap);
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return items;
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}
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rc = read_spec_entry(spec_entry, &buf_p, &entry_len);
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if (rc < 0) {
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va_end(ap);
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return rc;
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}
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if (entry_len) items++;
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}
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va_end(ap);
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return items;
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}
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bool ContextsSplit::MapSerialPropertyArea(bool access_rw, bool* fsetxattr_failed) {
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char filename[PROP_FILENAME_MAX];
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int len = async_safe_format_buffer(filename, sizeof(filename), "%s/properties_serial", filename_);
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if (len < 0 || len >= PROP_FILENAME_MAX) {
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serial_prop_area_ = nullptr;
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return false;
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}
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if (access_rw) {
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serial_prop_area_ =
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prop_area::map_prop_area_rw(filename, "u:object_r:properties_serial:s0", fsetxattr_failed);
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} else {
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serial_prop_area_ = prop_area::map_prop_area(filename);
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}
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return serial_prop_area_;
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}
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bool ContextsSplit::InitializePropertiesFromFile(const char* filename) {
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FILE* file = fopen(filename, "re");
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if (!file) {
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return false;
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}
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char* buffer = nullptr;
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size_t line_len;
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char* prop_prefix = nullptr;
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char* context = nullptr;
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while (getline(&buffer, &line_len, file) > 0) {
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int items = read_spec_entries(buffer, 2, &prop_prefix, &context);
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if (items <= 0) {
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continue;
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}
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if (items == 1) {
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free(prop_prefix);
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continue;
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}
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// init uses ctl.* properties as an IPC mechanism and does not write them
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// to a property file, therefore we do not need to create property files
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// to store them.
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if (!strncmp(prop_prefix, "ctl.", 4)) {
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free(prop_prefix);
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free(context);
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continue;
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}
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auto old_context = ListFind(
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contexts_, [context](ContextListNode* l) { return !strcmp(l->context(), context); });
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if (old_context) {
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ListAddAfterLen(&prefixes_, prop_prefix, old_context);
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} else {
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ListAdd(&contexts_, context, filename_);
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ListAddAfterLen(&prefixes_, prop_prefix, contexts_);
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}
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free(prop_prefix);
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free(context);
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}
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free(buffer);
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fclose(file);
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return true;
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}
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bool ContextsSplit::InitializeProperties() {
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// If we do find /property_contexts, then this is being
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// run as part of the OTA updater on older release that had
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// /property_contexts - b/34370523
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if (InitializePropertiesFromFile("/property_contexts")) {
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return true;
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}
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// Use property_contexts from /system & /vendor, fall back to those from /
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if (access("/system/etc/selinux/plat_property_contexts", R_OK) != -1) {
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if (!InitializePropertiesFromFile("/system/etc/selinux/plat_property_contexts")) {
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return false;
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}
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// Don't check for failure here, so we always have a sane list of properties.
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// E.g. In case of recovery, the vendor partition will not have mounted and we
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// still need the system / platform properties to function.
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if (access("/vendor/etc/selinux/vendor_property_contexts", R_OK) != -1) {
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InitializePropertiesFromFile("/vendor/etc/selinux/vendor_property_contexts");
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} else {
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// Fallback to nonplat_* if vendor_* doesn't exist.
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InitializePropertiesFromFile("/vendor/etc/selinux/nonplat_property_contexts");
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}
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} else {
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if (!InitializePropertiesFromFile("/plat_property_contexts")) {
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return false;
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}
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if (access("/vendor_property_contexts", R_OK) != -1) {
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InitializePropertiesFromFile("/vendor_property_contexts");
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} else {
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// Fallback to nonplat_* if vendor_* doesn't exist.
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InitializePropertiesFromFile("/nonplat_property_contexts");
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}
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}
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return true;
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}
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bool ContextsSplit::Initialize(bool writable, const char* filename, bool* fsetxattr_failed) {
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filename_ = filename;
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if (!InitializeProperties()) {
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return false;
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}
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if (writable) {
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mkdir(filename_, S_IRWXU | S_IXGRP | S_IXOTH);
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bool open_failed = false;
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if (fsetxattr_failed) {
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*fsetxattr_failed = false;
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}
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ListForEach(contexts_, [&fsetxattr_failed, &open_failed](ContextListNode* l) {
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if (!l->Open(true, fsetxattr_failed)) {
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open_failed = true;
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}
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});
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if (open_failed || !MapSerialPropertyArea(true, fsetxattr_failed)) {
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FreeAndUnmap();
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return false;
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}
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} else {
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if (!MapSerialPropertyArea(false, nullptr)) {
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FreeAndUnmap();
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return false;
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}
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}
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return true;
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}
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prop_area* ContextsSplit::GetPropAreaForName(const char* name) {
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auto entry = ListFind(prefixes_, [name](PrefixNode* l) {
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return l->prefix[0] == '*' || !strncmp(l->prefix, name, l->prefix_len);
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});
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if (!entry) {
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return nullptr;
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}
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auto cnode = entry->context;
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if (!cnode->pa()) {
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// We explicitly do not check no_access_ in this case because unlike the
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// case of foreach(), we want to generate an selinux audit for each
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// non-permitted property access in this function.
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cnode->Open(false, nullptr);
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}
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return cnode->pa();
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}
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void ContextsSplit::ForEach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
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ListForEach(contexts_, [propfn, cookie](ContextListNode* l) {
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if (l->CheckAccessAndOpen()) {
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l->pa()->foreach (propfn, cookie);
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}
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});
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}
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void ContextsSplit::ResetAccess() {
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ListForEach(contexts_, [](ContextListNode* l) { l->ResetAccess(); });
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}
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void ContextsSplit::FreeAndUnmap() {
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ListFree(&prefixes_);
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ListFree(&contexts_);
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prop_area::unmap_prop_area(&serial_prop_area_);
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}
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